Gaseous fuel (hereafter for simplicity, gas) burning devices, such as conventional hot water heaters and gas fireplaces, typically burn natural gas or propane. Pilot assemblies are conventionally mounted in, and used to light, such gas burning devices. A conventional pilot assembly includes a pilot which continuously burns gas at a low rate to provide a pilot flame. The pilot flame in turn lights an adjacent main burner when gas is supplied to the main burner.
As a convenient example of a conventional environment for such a pilot assembly, a conventional gas fireplace GF (FIG. 11) includes a floor 8, a fireplace box 9 extending upwardly from the floor 8, and conventional fireplace hardware 10 mounted in the fireplace box 9. The box 9 encloses sufficient volume for the fireplace hardware 10 and fireplace flames. The fireplace hardware 10 includes a grate 11 (in broken lines) standing on the floor 8, imitation noncombustible logs 12 (in broken lines) resting on the grate 11, a main burner 13 mounted to the floor 8 in substantially hidden relation behind the grate 11 and logs 12, and a pilot assembly 15. The main burner has plural gas flame producing nozzles 14, some adjacent the pilot assembly 15.
A typical conventional pilot assembly 15 (FIG. 12) includes a horizontal mounting bracket 17 fixed by any conventional means, not shown, with respect to the main burner 13. The pilot assembly 15 is substantially hidden behind the main burner 13. The assembly 15 includes a pilot 19, an ignitor 21, a thermocouple 22, and a thermopile generator 23, which are fixed on, and extend vertically through, the mounting bracket 17 in side-by-side relation.
The pilot 19 (FIG. 12) includes a one piece housing 27 extending vertically through and fixed to the central portion of the bracket 17. A semirigid, metal, gas supply tube 28 connects the bottom of the pilot housing 27 through a conventional pilot valve V to a conventional gas source GS. A typical pilot valve V is spring biased closed (to block gas flow to the pilot 19), but can be opened manually and can be held open electrically (to allow gas flow to the pilot). FIG. 12 schematically shows a suitable conventional pilot valve V comprising a spring biased closed valve core Cl interposed between the gas source GS and pilot supply tube 28, and a manual opener (e.g. push button) B1 and electromagnetic hold-open (e.g. solenoid) E1 actuatable to respectively open and hold-open the valve core C1 against its spring S1.
The upper end of the pilot housing 27 normally emits a pilot flame (not shown) fueled by gas supplied through the open valve V and tube 28. A pilot flame target 31 is fixed atop the housing 27 to direct the pilot flame laterally (to the right and left and forward out to the page in FIG. 12) along paths from the target 31. The top of the ignitor 21 (FIG. 12) is adjacent one side (the left side in FIG. 12) of the target 31, for igniting gas flow therefrom to establish the pilot flame of pilot 19. The tops of the thermocouple 22 and thermopile generator 23 closely flank the target 31 (FIG. 12), so as to be in the pilot flame path from opposite sides of the target 31 and with the ignitor 21 snugly spaced between the thermocouple 22 and target 31. The front of the flame target 31 is adjacent ones of the gas outlet nozzles 14 of the main burner 13, such that the forward directed flame pilot flame component ignites gas flowing from the main burner 13.
An electrically insulated wire 24 (FIG. 12) electrically couples the bottom of the ignitor 21 to the output of a conventional ignitor voltage source, here for example a conventional, manually actuatable, push button, piezo-electric voltage source PZ, grounded to the bracket 17. Given a supply of gas through the pilot valve V to the pilot 19, manual actuation of the piezo voltage source discharges an electrical spark between the tops of the ignitor 21 and pilot 19, thereby igniting the pilot gas flow and starting the pilot flame.
A relatively stiff wire 25 extends from the bottom of the thermocouple 22 to the control input of the electromagnetic hold-open E1 of pilot valve V. The thermocouple 22, when heated by the pilot flame from pilot 19, supplies a voltage (typically in the range of millivolts) to the solenoid E1 to maintain the valve V open and so maintain gas flow to the pilot and keep the pilot flame on. If the pilot flame becomes extinguished, the thermocouple 22 cools, its voltage output drops, and the solenoid E1 relaxes and the spring S1 closes the valve V and shuts off gas flow to the pilot 19.
The bottom of thermopile generator 23 (FIG. 12) connects through a heat shielded, relatively stiff, electrically insulated wire pair 26 to a main gas safety valve MV interposed between the conventional gas source GS and the main burner 13. The thermopile generator 23 responds to pilot flame heat to electrically open the main valve MV to supply gas from the gas source GS to the main burner 13 and responds to lack of pilot flame heat to close the valve MV and thus shut off gas flow to the main burner 13. The main safety valve MV may be a conventional solenoid valve (like pilot V but without the manual opener B1) comprising a valve core C2 spring biased closed by a spring S2 and openable by a solenoid E2.
Typically, a manual control MC, in the form of a manually adjustable valve, is in series with the main safety valve MV, between the gas source GS and main burner (MB) 13, to allow the human operator of the fireplace GF to turn on and off, and vary the flame height of, the main burner MB.
The top and bottom ends of the one-piece pilot housing 27 (FIG. 13) are spaced above and below the bracket 17. The housing 27 has a radially inwardly stepped, upper housing portion 45. The housing 27 also has a stepped axial through passage 29. The passage 29 has a substantially cylindrical top portion 42, an enlarged-diameter midportion 43 and a further enlarged-diameter, bottom opening, internally threaded recess 44. The portions 42 and 43 are separated by a tapered annular step 46. The midportion 43 and recess 44 are separated by an annular step 47, the upper portion of which is tapered upward and inward. The open top 48 of the passage 29 acts as the ignited gas/air mixture (flame) outlet nozzle of the pilot 19.
The pilot flame target 31 comprises a semi-circular base 38 which is fixed, by any convenient means, such as welding, to the upper housing portion 45. The target 31 has an inverted trough-like, pilot flame deflector 39 fixedly upstanding from the base 38 and spaced above the pilot flame outlet nozzle 48 for deflecting the pilot flame laterally (to the left and right in FIG. 13) toward the ignitor 21, thermocouple 22 and thermopile generator 23 and forwardly (out of the page in FIG. 13) toward the main burner 13.
At least one air supply aperture 32 opens radially through the peripheral wall of the housing 27 and into the midportion 43 of the passage 29. The aperture 32 may be above the bracket 17 as here shown, or below it.
An inverted cup-shaped, pilot orifice-containing member 33 includes a substantially cylindrical peripheral wall 35, a horizontal top end wall 36, a central orifice 34 preferably centered in the end wall 36, and a radially outwardly and downwardly flared bottom flange 40. The orifice member 33 is assembled in the pilot housing 27 by upward insertion through the threaded bottom recess 44. When so installed, as seen in FIG. 9, the top end wall 36, with its orifice 34, is located closely below the air aperture 32, the peripheral wall 35 is in snug sliding engagement with the lower portion of the passage midportion 43, and the bottom flange 40 snugly abuts the tapered step 47.
An upper end of the pilot gas supply tube 28 is fixedly tipped by a ferrule 37 (FIG. 13) that is tapered at its upper and lower ends 51 and 52.
A spool-like, annular fitting 41 (FIG. 13) is snugly but axially and rotatably slidably sleeved on the gas supply tube 28 below the ferrule 37. The fitting 41 adjacent its lower end has a wrench-engageable (here hexagonal) rim 53. The fitting 41 is externally threaded at 54 adjacent its upper end and includes a central throughbore 55. The upper end of the fitting throughbore 55 is tapered at 56. The gas supply tube 28 is fixed to the bottom of the housing 27 by inserting the ferrule 37 into the housing bottom recess 44 until it rests against the tapered bottom flange 40 of the orifice member 33. The fitting 41 is then threaded into the threaded bottom recess 44 of the housing 27. Threadedly tightening the fitting 41 axially presses it, fitting taper 56 to ferrule taper 52, against the bottom of the ferrule 37 and in turn axially upwardly presses the ferrule 37 so that its upper taper 51 forcibly presses the bottom flange 40 against the tapered step 47 of the housing 27. This locks in place the orifice member 33 in the housing 27 and prevents leakage of gas, such that all gas from the gas supply tube 28 must pass up through the orifice 34 and mix with air from the aperture 32, and such that the resultant gas/air mixture must pass upwardly through the passage top portion 42 and out the nozzle 48 for ignition and production of the pilot flame.
However, different fuel gases differ in energy content and so require different sized orifices 34 to supply gas at different flow rates for maintaining the desired size pilot flame. Manufacturers, retailers, and repair persons must thus inventory different pilot assemblies 15 (FIG. 12) for different gaseous fuels, or must change the orifice member 33 (FIG. 13) in a given assembly if a different fuel gas than originally contemplated is to be used. Unfortunately, inventorying different pilot assemblies 15, and more importantly appliances incorporating them, is space consuming and expensive.
Also, unfortunately, in such prior pilot assemblies 15 (FIG. 12), changing the orifice member 33 (FIG. 13) is difficult and time consuming because access to the orifice member 33 is difficult before, and particularly after, the conventional pilot assembly 15 is installed in a gas burning device, for example a fireplace or water heater. More particularly, to remove the existing pilot orifice member 33, the fitting 41 and gas supply tube 28 must be removed from the bottom of the pilot 19. However, access to the fitting 41 is usually, at least partially, blocked, e.g. by the bracket 17 and main burner 13, if not additionally by user device structure, such as the nonflammable logs 12, grate 11 or fireplace box 9 (FIG. 11). Further, the stiffness of the gas supply tube 28 requires either that it be bent (thus risking kinking and disabling) away from the pilot 19, or that the bracket 17 be disconnected from supporting structure of a user device and that the relatively stiff electrical conductor members 25, 26 also be disconnected to enable access to the bottom of the pilot 19.
U.S. Pat. No. 6,027,335, filed Feb. 3, 1999 (Attorney Reference: PSE Case 1), by the owner of the present application, discloses an improved pilot assembly which effectively avoids prior art disadvantages such as those above discussed, e.g. by allowing access to the orifice member from above the mounting bracket and so greatly easing exchanging one orifice member for another to adapt the pilot assembly to gaseous fuels of different characteristics. While that improved pilot assembly has been successful in use and has rapidly gained interest in the marketplace, nonetheless a program of continuing development and improvement has now led to the present invention.
Accordingly, objects of the present invention include providing a pilot assembly having more efficient and easier conversion of the pilot orifice, and hence the pilot, from one gaseous fuel to another.